Draft gear



K. G. EMPSON DRAFT GEAR Filed July 16, 1963 Julie 1, 1965 INVENTOR. KENNETH G. EMPSON %///M/////A// d 8 mm m m N $1 I W saM/wfld ATTORNEYS United States Patent 3,186,563 l ii lg S Jose Calif K ethG.Em son 1 2 an elm Filed Jui 16, 1963, S61. No. 295,493

2 Claims. (curs-43 This invention relates to a draft gear for use n a railroad coupler and more particularly relates to an I p ment in the draft gear embodying a combination of rubber spring and hydraulic shock absorbing means as Set forth in my co-pending patent application Serial No. 186,923 filed April 12, 1962 now patent 3,135,394. In said patent application I described and claimed a railroad draft gear wherein the buff andd raft strokes can be individually varied so that the draft stroke can be made stiffer than the buff stroke. In said invention the draft gear has rubber springs on both sides of a hydraulic cylinder, the rubber springs giving a high mechanical capability to the unit so that it does not close out going either up or down a steep gradient, while the hydraulic system takes up sudden changes as in coupling. Thus, the hydraulic system is adapted to absorb impacts and shocks while the rubber spring system is adapted to maintain control under conditions of sustained buff or draft.

In said system the hydraulic cylinder is preferably made with a taper so that the center portion had a relatively loose fit while there was a relatively tight fit at either end of the hydraulic cylinder.

When some of the cars of a train are fitted with conventional draft gears while others are fitted with the above described gear the hydraulic portion of the improved gear does not function as intended so that the rubber springs must take up most of the shock of the impact since a conventional draft gear cannot instantly transmit all the force of an impacting car. Because of this, the hydraulic draft gear travels approximately 70% of its strike before it receives the full force of the impact.

In accordance with the present invention, this condition is remedied by providing a cylinder having a portion opposite the piston at rest of reduced diameter so that there is a relatively tight fit of the piston when at rest. With such a structure the velocity of the fluid remains constant, therefore giving a constant reactive force level against the coupler. This has the effect of making the conventional draft gear close out before the hydraulic draft gear, therefore leaving most of the stroke to absorb the force of the impact. Just olf the reduced diameter portion the fit is made relatively loose. Tapers may extend toward both ends of the cylinder so that the piston travels near the end to maintain constant fluid pressure and velocity.

The sole figure of the drawing is a side sectional view of a coupler embodying the present invention and corresponds generally to FIGURE 2 of the above mentioned application Serial No. 186,923 filed April 21, 1962.

Referring now to the drawing by reference characters there is shown a center sill 21 which forms part of the frame of a railway car. Front stops 16 and rear stops 18 form a pocket for the reception of the draft gear which has been generally designated 20. Yoke 22 fits around the draft gear 20. The yoke 22 has a top member 24, a bottom member 26 and a rear end member 28. The yoke 22 extends forward and terminates in cars, one car 30 being shown, the opposite car not being visible in this view. The yoke has a slot adapted to receive a conventional key 34. Extending forward from the yoke is a draft bar 36 having an elongated slot 40 therein which passes over the key 34. Thus, as a car 3,186,563 Patented June 1, 1965 "ice is pulled in draft the key 34 will engage the rear of the slot 40, tending to pull the yoke forward, in turn tending to compress the draft gear 20, stressing it against the shoulder 16 and thus transferring the forward motion of the car. On the other hand, during coupling or stopping, the draft bar 36 will not transmit force through the yoke but the draft bar will be pressed against draft gear 20 transmitting the force through the draft gear and to the rear stop 18.

Referring now to the draft gear proper, the structure is generally that disclosed in my prior patent application and comprises a central cylindrical portion 42 having a piston 44 therein which is attached to the piston rod 46. The ends of the cylinder 42 are designated 48 and 50 and are provided with sealing rings 52 and 56 it being understood that the cylinder 42 is substantially filled with a suitable hydraulic fluid such as oil. Rubber springs 58 and 60 are provided at each end of the cylinder for taking up the gradual stresses produced under relatively steady buff and draft conditions; the buff springs 58 would normally be made stiffer than the draft springs 60. The exact structure of the springs forms to part of the persent invention but generally speaking they are constructed in accordance with my previously mentioned co-pending patent application.

In the cylinder 42 the center section is provided with an annular portion of reduced diameter as at 62, with portions of increased diameter as at 64 and 66 on each side thereof. Further the cylinder walls taper toward each end so that at the ends 70 and 72 the diameter of the cylinder is substantially the same as that of the reduced center portion. By employing this structure, there is a very substantial resistance to movement under sudden shocks in either direction when the piston is at the center of the path of travel. Thus in a coupling operation, the reduced diameter of the cylinder at the center would provide a substantial resistance to movement. However, after some movement has taken place, the resistance becomes lessened due to the increased diameter portion of the cylinder yet, if the force continues so that the piston is forced to either end of its path of travel, the resistance stilfens towards the end so that the device is capable of absorbing extremely severe shocks. Thus the device of the present invention is able to absorb extremely heavy shocks yet dissipates such shocks over a substantial path of travel if force is continued on the device.

In the drawing and above description, the piston is shown at rest in the center of the cylinder. This design is for a unit having buff and draft strokes of the same length. Under some conditions, the unit might be designed for unequal stroke lengths, so that the position of the piston would be at one side or the other of center. With such units, the reduced diameter portion of the cylinder must be moved off center so that it will be opposite the position of the piston at rest. Additionally, it should be observed that the drawing is grossly exaggerated for purposes of illustration. In one practical embodiment of the invention the diameter of the cylinder was reduced by 0.0015 inch opposite the piston.

I claim:

1. In a buffer for a railroad draft gear comprising a combination of a hydraulic cylinder with rubber buff and draft springs mounted in a unit adapted to fit within the yoke of a railroad coupler, the improvement comprising a hydraulic cylinder having a piston therein, said piston normally under conditions of rest riding at a point between the ends of the cylinder, and a reduced 3 4 annular intermediate portion in said cylinder opposite References Cited by the Examiner the position of the piston at rest whereby a relatively UNITED STATES PATENTS small clearance exists between said cylinder and said piston when the piston is at rest with a greater clearance g g on either side of said reduced annular portion. 5 P Deer e a 2. The structure of claim 1 wherein said piston tapers FOREIGN PATENTS at both endsthereof forming end sections of reduced 499 451 11 /5 B l i diameter, said end sections having substantially the same diameter as said intermediate section. LEO QUACKENBUSH, Primary Examiner. 

1. IN A BUFFLE FOR A RAILROAD DRAFT GEAR COMPRISING A COMBINATION OF A HYDRAULIC CYLINDER WITH RUBBER BUFF AND DRAFT SPRINGS MOUNTED IN A UNIT ADAPTED TO FIT WITHIN THE YOKE OF A RAILROAD COUPLER, THE IMPROVEMENT COMPRISING A HYDRAULIC CYLINDER HAVING A PISTON THEREIN, SAID PISTON NORMALLY UNDER CONDITIONS OF REST RIDING AT A POINT BETWEEN THE ENDS OF THE CYLINDER, AND A REDUCED ANNULAR INTERMEDIATE PORTION IN SAID CYLINDER OPPOSITE THE POSITIONOF THE PISTON AT REST WHEREBY A RELATIVELY SMALL CLEARANCE EXISTS BETWEEN SAID CYLINDER AND SAID PISTON WHEN THE PISTON IS AT REST WITH A GREATER CLEARANCE ON EITHER SIDE OF SAID REDUCED ANNULAR PORTION. 